Lots of "Database is locked" log lines

[stellarpower]

Hi,

Currently on version 0.8.1; I've seen "Database is locked" messages come up before - initially they were sporadic and usually went away, but now they seem to be persistent. My users are unable to log into their IMAP and the server is also rejecting incoming messages with a 50x, so we are losing quite a lot of traffic.

Generally I have the logging turned up high, but there isn't much in there to tell me what's going on without trying to attach a debugger. Please could you advise what log directives would be best to add to see if I can pinpoint what might be going on? I have done some source-level work with Maddy but none of it affecting the database, so as there ought to be multiple places/portions of the configs where it will be involving the database, thought you would have a much better idea of what logging to turn up to the max.

Thanks a lot